Method of heat-treating a swellable bentonite to increase its thickening power



Patented Sept. 16, 1952 METHOD OF HEAT-TREATING A SWELL- ABLE BENTONITE TO INCREASE ITS THICKENING POWER Francis E. Hutchins, East Norwalk, and Glen J. Golding, South Nor-walk, Conn... assignors to R. T. Vanderbilt 00., Inc.

No Drawing. Application August 17, 1950, Serial No. 180,077

This invention relates to a method for enhancing the capacity of a swellable bentonite to increase the viscosity of aqueous dispersions thereof.

Bentonite is a clay-like mineral which is noted for its very fine grain size. its high absorptive properties and its high plasticity. As a'result. it has found application as a suspending, thickening and paste-forming agent in a wide variety of aqueous compositions, including cosmetic. pharmaceutical and industrial suspensions and emulsions. In the. copending application of William K. Feustel and Francis E. Hutchins. vSerial No, 765,804, flled August 2, 1947, now United States Patent No. 2,523,20i, there is described a bentonite composition which is particularly useful in the manufacture of various aqueous preparations. This composition is composed of an intimate admixture of fine, grit-tree constituents of a high gel magnesium bentonite, a high gel aluminum bentonite, and amedium gel aluminum bentonite in the proportions of from 5 to parts by weight .of the magnesium bentonite, from to 60 parts by weightof the high gel aluminum bentonite and from to "70 parts by weight of the medium gel aluminum bentonite. The composition is treeof particles which are sufficiently coarse to make the composition gritty.

When using bentonite as a viscosity increasing or thickening agent, it is desirable to use as little as possible, in order to decrease the cost of the final mixture. We have discovered a method whereby this can be accomplished, the method being a procedure whereby the thickening power of abentonite in powder or flake form can be increased. This procedure comprises maintaining the bentonite, when containing absorbed water, at a somewhat elevated temperature until the desired increase in thickening power has taken place.

The following examples illustrate in detail the practice of the present invention. In these examples, viscosities are measured in Brabender units.

Example .I

Asample oi a commercially available Wyoming bentonite was dispersed in water. drum dried and the dried material flaked. A 3.8% by weight aqueous dispersion of a portion of the flakes had an immediate viscosity of 210. The remaining flakes were maintained at a temperature of 50 C. for a period of time. At the end of eight days, the flakes contained 3.4% by weight of moisture and a 3.8% by weight aqueous disper- 3 Claims. (01. coc -s17) sion of a portion of the flakes had a viscosity of 250. At the end of seventeen days, the flakes contained 3.0% by weight of moisture and a I by weight aqueous dispersion of a portion of the flakes had a viscosity of 270.

Example II A sample of a commercially available bentonite was dispersed in water using a ball mill to form a dispersion containing 12% by weight of solids. This dispersion was centrifuged at a centrifugal force of about one thousand times that of gravity in such a manner that 72% by weight of the bentonite taken passed through the screen. to cther with the water, while th remainder of the bentonite was retained in the basket of the centrifuge. The aqueous dispersion containing 7.2% by weight of the bentonite taken was then drum dried and the dried bentonite flaked.

A 4.1% by weight aqueous dispersion of a portion of the flakes had an immediate viscosity of 230,. The remaining flakes were maintained at a temperature of 50 C. for a period of thirty- .five days. At the end of eight days, the flakes contained 3.4% by weight of moisture and a 4.1% by weight aqueous dispersion of a portion thereof ,had a viscosity of 310. At the end of thirty-five days, the flakes contained 0.4% by weight of moisture and a 4.1 by weight aqueous dispersion of a portion thereof had a viscosity of 305.

Example III A sample of Roberts bentonite was dispersed in water and the dispersion centrifuged as described in Example II. In this case, however. 76% by weight of the sample taken was re covered and formed into flakes.

A 5.0% by weight aqueous dispersion of a portion of the flakes had an immediate viscosity of 160. The remaining :fiakes were maintained at a temperature of 50 .C. At the end of eight days, a 5.1% by weight aqueous dispersion of a portion of the flakes had .a viscosity of 220. .At the end of thirty-five days, the flakes contained 3.0% by weight .of moisture and a 5.0% by weight aqueous dispersion of aportion of the flakes had a viscosity of 2. .5. p a

Example IV Using the procedure described in Patent No. 2,523,204, there was prepared a 12% by weight aqueous dispersion of a mixture of bentonites, the bentonites being a high gel magnesium bentonite, a high gel aluminum bentonite and a medium gel aluminum bentonite in the weight was 61.1% by weight of silicon dioxide, 13.7%

by weight of magnesium oxide, 9.3% by weight of aluminum oxide, 0.1% by weight of titanium dioxide, 0.9% by weight of ferric oxide, 2.7%

by weight of calcium oxide, 2.9% by weight of sodium oxide, 0.3 by weightof potassium oxide, and 1.8% by weight of carbon dioxide. The mixture contained 7.2% by weight of water of 4 those skilled in the art. In practicing the present process, it is critical, however, that the bentonite subjected to the aging treatment at the somewhat elevated temperature contain absorbed moisture, preferably in the amount ofgat least 0.5% by weight, based upon the weight of the bentonite. The upper limit of moisture content is not critical, so long as the bentonite remains combination, was white in color and contained about 8% by weight of moisture.

A 5.0% by weight aqueous dispersion of a portion of the flakes had an immediate viscosity of 155. The remaining flakes were maintained at a temperature of 92. C. for a period'of time. At the end of two weeks, the flakes contained 1.0% by weight of moisture and a 5.0% by weight aqueous dispersion of a portion thereof had a viscosity of 585. At the end of four weeks; the flakes contained 0.5% by weight of moisture and a 5.0% by weight aqueous dispersion of a portion thereof had a viscosity of 6 25. l

s i 1 Example V A batch of flakes was prepare'd in the manner described in ExampleIV but in this'case the recovery from the centrifuging operation was 61.0 byweightk 1 A 5.0% by'weight aqueousdispersion of a 'portioncf the flakes had an immediate viscosity'of 130. The remaining flakes were maintained at a temperature of 50 C. for aperiod of eight weeks. At the end of one week, the'flakes contained 3.5% by weight of moisture and a 5.0% by weight aqueous dispersion of aportion thereof had a viscosity of 315. At the end of two weeks, the flakes'contain ed 2.9% by weight of'moisture and a 5.0% by weight aqueous dispersion had a viscosity of 380. At the end of eight weeks, the flakes contained 2.9% by weight of moisture and a 5.0% by weight aqueous dispersion'had a viscosityof 690. a f

' w gvi.

A batch of flakes was prepared in the manner described in ExampleIV, but in this case, the recovery after the centrifuging operation was 62.5% by weight. I

A 5.0% by weight aqueous dispersion of a portion of the flakes had an immediate viscosity of 160. The remaining flakes were maintained at a temperature of 42C. for a period of eight weeks. At the end of one week, the flakes contained 6.5% by weight of moisture and a 5.0% by weight aqueous dispersion had a viscosity of 270' At the end of; two weeks, theflakes contained 6.3% by weight of moisture and a 520% by weight aqueous dispersion had a viscosity of 295. At the end of eight weeks, the flakes contained 4.8% by weight of moisture and a 5;0% by weightaqueous dispersion had a viscoity of 355.

Various modifications can be made in the speciflc procedures described, as will be apparent to inthe form of flakes or powder. As the specific examples illustrate, increased temperatures result in an increase at which the thickening power takes place, and therefore temperatures of at least aboutAOfgGshould be used for the aging, temperaturesof 50 to 100 C. being preferred.

The aging should be carried out for a period of time suflicient to effect a substantial increase in the thickening power of the bentonite, and this usually requires at least about one week.

'As the examples illustrate, the method described is useful for the purpose of increasing the thickening power of thebentonite mixture described in Patent No, 2,523,204. This mixture is free 1 of particles substantially'coarse to impart grittiness and contains from 5 to 15 parts by weight of high: gelmagnesium bentonite, )20' to 60 parts by weight of high' gel aluminum benton ite and to 70 parts by weight of medium gel aluminum bentonite. 1 .We'claim: v

' l; A process for increasing the thickening power of a swellable" bentonite when incorporated into aqueous dispersions, the said "methodcom prising -maintaining'--the bentonite in flake or powder form at a temperatu'reof at'l'east about 40 Cmand not more than about -1'ooc.ror' a period of at least j one weekwill the bentonite contains absorbed'wat'er. r f s '2.'-A method as in'claiml in which the ben tonite 1 contains at least "about -0.5 :bTWGightof st i I'. .1 i.

A method as in claim '1" in which the bento n ite is an intimate admixtureo'f fine, grit free constituents Offfi, high'gel "magnesiumbentonitea highgel aluminum bentoniteand' a medium gel aluminum bentonite-in the-proportions 01mm 5 to 15 partsby weight of the magnesium bentonf ite, from 20 toparts by weight of-the'j high gel aluminum bentonite and from 30 to '70 parts by weight of the medium gel aluminum bentonite. 1 HUToHINs. a CLEOI L I G."

g REFERENCES CITED j The following references areiof record in the flle of this patent! f f I v UNITED STATES-PATENTS Number Name 7' Date OTHER, Ea Ncgs'f-j Y Mellor: .CompreliensiveTreati'se on ln'organic 

1. A PROCESS FOR INCREASING THE THICKENING POWER OF A SWELLABLE BENTONITE WHEN INCORPORATED INTO AQUEOUS DISPERSIONS, THE SAID METHOD COMPRISING MAINTAINING THE BENTONITE IN FLAKE OR POWDER FORM AT A TEMPERATURE OF AT LEAST ABOUT 40* C. AND NOT MORE THAN ABOUT 100* C. FOR A PERIOD OF AT LEAST ONE WEAK WHILE THE BENTONITE CONTAINS ABSORBED WATER. 